I know I quote him often, but he keeps publishing awesome content, what else am I going to do? From Seth Godin:

Before you design a chart or infographic

What's it for?

A graph only exists to make a point. Its purpose is not to present all the information. Its purpose is not to be pretty.

Most of all, its purpose is not, "well, they told me I needed to put a graph here."

The purpose of a graph is to get someone to say "a-ha" and to see something the way you do.

Begin there and work backwards.